The separation of the service layer and the bearer layer further requires effective control on bearer resources based on certain policies. According to the network architecture designed by major international standardization organizations, the bearer resources required by services are met through management of bearer resources by a bearer control layer. A bearer resource control network is shown in FIG. 1, where, a service control function (SCF) is located at the service layer, a network attachment control function (NACF), a resource and admission control function (RACF) are placed at the bearer control layer of the bearer layer, and a transport function (TF) is at the bearer resource layer of the bearer layer. The RACF further includes a policy decision functional entity (PD-FE) and a transport resource control functional entity (TRC-FE). The TF further includes a policy execution functional entity (PE-FE) and a transport resource execution functional entity (TRE-FE).
When a user service requires a bearer resource, the SCF sends a service requirement to the PD-FE in the RACF. The PD-FE obtains resource status from the TRC-FE, forms a resource provision decision according to a certain policy, and delivers the resource provision decision to the PE-FE for execution so that the required resource is provided for the service. For such a decision to be delivered from the PD-FE to the PE-FE, two modes are necessary: one is that the PD-FE sends the decision configuration on the provision of the related resource to the PE-FE actively, known as the Push mode which is relative to the PD-FE; the other is that the PD-FE sends a decision on the provision of the related resource in response to a request of the PE-FE, known as the Pull mode which is relative to the PE-FE.
H.248 is gradually becoming a mainstream protocol in bearer control, especially for the interface between PD-FE and PE-FE. When H.248 is applied to the interface between PD-FE and PE-FE, the PE-FE is equivalent to an MGC and the PE-FE is equivalent to an MG. However, the primary control model of H.248 now is that the MGC manager resources on the MG. This means the MGC delivers resource provision decisions to the MG actively according to the service requirement information of users and/or resource status. As a result, the method provided by H.248 for an MGC to deliver resource provision decisions to an MG only supports the Push mode. The Pull mode, however, is not supported. The service requirement information may be media stream information and/or user information.
In addition, in the foregoing method for an MGC to deliver resource provision decisions to an MG actively, if the MG does not receive a media stream establishing request from the user immediately after the MGC delivers a resource provision decision to the MG so as to execute the resource provision decision to establish a media stream, the MG needs to store the resource provision decision for the period before reception of the media stream establishing request. This will occupy the limited storage space in the MG, and the decision may not be suitable for the service requirement and resource status when the resource provision decision is finally executed.